Coffee is acidic. The pH of coffee measures the degree of its acidity or basicity (alkalinity), and is expressed on a scale of 0 to 14. The pH of coffee typically ranges from 4.85 to 5.10, as determined by a 2018 study published in Scientific Reports, although some variations exist. Roasting temperature, brewing temperature, and type of coffee bean are factors that affect the pH of coffee.
So, why is coffee acidic? The acidity of coffee is due to the presence of acidic molecules like chlorogenic acid, quinic acid, and citric acid. These molecules, according to a 2009 study in the Journal of Agricultural and Food Chemistry, are not only preserved but often enhanced during the roasting process, with lighter roasts generally being more acidic than darker roasts.
Interestingly, according to a 2007 study published in the Journal of The Science of Food and Agriculture, there is no correlation between coffee pH and perceived acidity in the flavor of coffees, but rather with titratable acidity, a measure of the total amount of acid present in coffee. However, for some individuals, particularly those with conditions like gastritis, acid reflux, or IBS, the high acid content of coffee can cause discomfort and potential health issues. Various coffee drinks have different pH levels, with decaf black coffee, espresso, cold brew, doppio, and americano tending to be more acidic than those with added milk, like lattes and cappuccinos. However, even with milk, coffee remains an acidic beverage.
While the low-acid coffee trend is on the rise, a 2023 study from North Carolina A&T State University found that some coffee brands labeled as "low acid" may not be significantly less acidic than regular coffees. For those seeking low-acid coffee, opting for dark roast whole bean coffee is generally recommended.
What Is pH?
pH is a measure of the hydrogen ion concentration in coffee, using the pH scale, which ranges from 0 to 14. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic (or alkaline). Coffee typically ranges from about 4.85 to 5.10, making it slightly acidic.
In scientific terms, pH is equal to the negative logarithm (base 10) of the hydrogen ion concentration in a solution, as defined by Erin Hopkins in "Physiology, Acid Base Balance." This means that a lower pH indicates a higher concentration of hydrogen ions (H+), and thus, higher acidity. In simpler terms, the pH scale measures the balance between hydrogen ions (H+) and hydroxide ions (OH-) in a solution like coffee.
The term pH stands for 'potential of hydrogen' or 'power of hydrogen.' While the exact origin of the "p" is debated, it may refer to the French "puissance," the German "Potenz," or the Danish "potens," all meaning "power." Regardless of its precise meaning, Danish chemist Søren Sørensen introduced the concept of pH in 1909, revolutionizing our understanding of acidity and basicity in solutions.
The primary ions used to measure the pH of coffee are hydrogen ions (H+) and hydroxide ions (OH-). When coffee contains more hydrogen ions, it's acidic. Conversely, coffee with more hydroxide ions is basic.
The pH scale is logarithmic, not linear. This means each unit change represents a tenfold difference in acidity. For example, coffee with a pH of 4 is ten times more acidic than coffee with a pH of 5, and a hundred times more acidic than coffee with a pH of 6. This graph provides a visual representation of the acidity or alkalinity using pH scale of common aquatic substances, including coffee.
What Is the pH of Coffee?
The pH level of coffee varies depending on several factors, including the brewing method, coffee bean type, and whether the coffee is hot or cold brewed. Generally, hot brewed coffee has a pH range of 4.85 to 5.10, while cold brew coffee is marginally less acidic, with a range of 5.40 to 5.63. This difference was observed in a 2018 study in Scientific Reports, where researchers from the Department of Chemistry and Biochemistry at Thomas Jefferson University found that cold brew coffee had a slightly higher pH level (and thus lower acidity) on average, about 2.80% higher than hot brewed coffee.
Different brewing methods influence the pH level of coffee. A 2013 scientific study in European Food Research and Technology compared various methods, including semi-automatic and fully automatic espresso machines, single-serve capsules, filter coffee, and French press. The pH values ranged from 5.51 to 5.92, with French press producing the least acidic coffee (pH 5.92) and single-serve capsules the most acidic (pH 5.51).
The type of coffee bean plays a role in how acidic coffee is and its pH level. A 2007 study published in the Journal of the Science of Food and Agriculture found that Arabica coffees tended to have lower pH values (5.2 to 5.8), indicating higher acidity, compared to Robusta blends when brewed as espresso under fixed conditions (92°C water temperature, 9 ATM pressure, 21s extraction time, and 38mm filter diameter).
Numerous factors determines both the pH of coffee and its acidity, including roasting temperature, brewing temperature, chemical composition, water quality, extraction method, water-to-coffee ratio, grind size, and brewing equipment, as illustrated in this table.
| Factor Affecting Coffee pH Levels | Description | Reference |
|---|---|---|
| Roasting Temperature | Higher roasting temperatures (above 200°C/ 392°F) generally decrease the acidity, brightness, and body, and increase the pH of coffee. Dark roast coffee, such as French or Italian roast, is less acidic and have higher pH values compared to lighter roasts like cinnamon, blonde, or light city roast. | Journal of Agricultural and Food Chemistry (2009) |
| Brewing Temperature | Cold brewing methods like immersion, slow drip, or Kyoto-style generally result in a slightly higher pH levels and less acidity compared to traditional hot brewing methods like pour-over, drip, percolation, or espresso. | Scientific Reports (2018) |
| Type of Coffee Bean | The origin, altitude, type, and varietal of coffee beans affects coffee acidity and pH. Arabica beans from Ethiopia, grown at 2,000 meters above sea level, have lower pH and are generally more acidic than Robusta beans from Vietnam, grown at 500 meters above sea level. | Food Research International Journal (2019) |
| Chemical Composition | The varying presence of chlorogenic, citric, acetic, formic, malic, quinic, pyruvic, succinic, and other organic acids in green coffee beans before and after roasting plays a significant role in determining the acidity, sourness, and pH of the coffee. | Journal of Agricultural and Food Chemistry (2009) |
| Water Quality | The amount and type of minerals (calcium, magnesium, and bicarbonate) in brewing water, type of water (tap, bottled, and filtered), and pH of the brewing water can directly impact the final pH of the coffee. | Environmental Health Insights (2023) |
| Extraction Method | pH of coffee changes with different brewing methods (drip, immersion, espresso) affecting the coffee acidity and taste due to variations in extraction pressures, temperatures, and times. | European Food Research and Technology (2013) |
| Water-to-Coffee Ratio | A higher water-to-coffee ratio typically results in a less concentrated brew, which can slightly affect the pH. | European Food Research and Technology (2013) |
| Grind Size | Grind size affects extraction rates and overall flavor but does not significantly impact the pH of the coffee. | Scientific Reports (2019) |
| Brewing Equipment | The material and cleanliness of the brewing equipment can influence the pH. Metal equipment might slightly alter the pH compared to glass or ceramic. | Foods Journal (2023) |
Is dark roast coffee more acidic? Dark roast coffee is generally perceived as less acidic, not more, due to the breakdown of citric and malic acids during roasting. However, things that make coffee acidic are not limited to those acids.
What Makes Coffee Acidic?
Coffee is acidic due to a combination of factors, including a pH level below 7 and the presence of various organic acids like citric acid, malic acid, quinic acid, acetic acid, formic acid, lactic acid, chlorogenic acids (CGAs), and tartaric acid.
- Citric Acid: Citric acid is one of the most prominent acids in green coffee, contributing to its bright, fruity acidity. Arabica coffee typically contains higher amounts of citric acid than Robusta, but concentrations decrease significantly during roasting, according to a 2019 study in Royal Society of Chemistry. In green Arabica coffee, citric acid can reach levels as high as 1.3 g/kg.
- Malic Acid: Malic acid is a key acid in green coffee, known for adding a smooth, apple-like tartness, as per a 1999 study in Chemistry and Environmental Science. Similar to citric acid, its concentration decreases with roasting. Green Arabica coffee has around 1.2 g/kg of malic acid, but roasting can reduce this to below 0.5 g/kg, impacting the perceived acidity, as noted by Michael Ginz in a study published in the European Food Research and Technology journal in January 2000.
- Quinic Acid: Quinic acid refers to an organic acid found in coffee beans that contributes to the bitterness and astringency of the brew. Quinic acid levels increase significantly during the roasting process, particularly in darker roasts, due to the breakdown of chlorogenic acids. This increase in quinic acid not only enhances the perceived bitterness but also contributes to the complex flavor profile of the coffee, adding depth and astringency.
- Acetic Acid: Acetic acid is a byproduct of the roasting process, which, according to a 2008 study in the Journal of Agricultural and Food Chemistry, contributes to a vinegar-like sourness and a pungent aroma. Dark roasted Robusta coffee can contain up to 10 times more acetic acid than green coffee, with concentrations exceeding 2.0 g/kg (Ginz et al., 2000). This significant increase is due to the breakdown of carbohydrates like sucrose during roasting.
- Formic Acid: Formic acid is a naturally occurring organic acid, and although present in smaller amounts in coffee, adds a sharp, pungent sourness to coffee, as noted by Pam Hartwig in a 2006 study published in the Journal of Food Science. Formic acid levels are notably higher in Robusta coffee, particularly after roasting, with dark roasts containing up to 0.5 g/kg. This acid forms primarily through the degradation of sugars and other organic compounds during high-temperature roasting.
- Lactic Acid: Lactic acid is a naturally occurring organic acid found in coffee beans, and is less affected by roasting compared to other acids, maintaining a consistent level that contributes to the smoothness and mild acidity of the brew, according to a 1995 study titled "Flavor Characteristics of Lactic, Malic, Citric, and Acetic Acids at Various pH Levels" in the Journal of Food Science. In both green and roasted Arabica coffee, lactic acid concentrations hover around 0.3 to 0.4 g/kg. Its stable presence helps in balancing the overall acidity and mouthfeel of the coffee, making it a key component in the complex flavor profile of coffee, according to researchers from the U.S. Department of Agriculture (USDA).
- Chlorogenic Acids (CGAs): Chlorogenic acid is a group of polyphenol compounds, and particularly 5-caffeoylquinic acid (5-CQA), are abundant in green coffee beans. During roasting, these CGAs degrade into various compounds, including quinic and caffeic acids, which contribute to the coffee's complex acidic and bitter profile. Arabica coffee, for example, can contain up to 8 g/kg of 5-CQA in its green beans, but this amount is significantly reduced during roasting (Vignoli et al., 2014).
- Tartaric Acid: Tartaric acid is a naturally occurring organic acid that is present in many fruits, most notably grapes, and is present in lower concentrations, adds a sour taste and enhances fruit flavors in coffee, according to experts at The Good Scents Company Information System. In green Robusta coffee, tartaric acid levels are about 0.2 g/kg, which generally decreases slightly after roasting as per a 1999 study in Chemistry and Environmental Science. This acid plays a subtle role in the overall flavor enhancement, particularly in fruity coffee profiles.
These compounds collectively contribute to the enhanced acidic profile observed in caffeinated and decaffeinated coffee. Decaf coffee, similarly to regular coffee, is acidic, as it still retains many of the same acids, such as citric, malic, and quinic acids.
Is Decaf Coffee Less Acidic?
Decaf brewed coffee generally tends to be slightly less acidic than regular brewed coffee, mainly due to the higher levels of chlorogenic acids after roasting. However, the acidity of decaf varies depending on the bean type and the decaffeination process itself. For example, a 2016 study in European Food Research and Technology found that decaffeinated Robusta green coffee beans were slightly more acidic (pH of 4.63), while regular Robusta green coffee beans had a pH of 4.47.
A 2024 study published in Food Chemistry found that decaffeinated green coffee beans had a 10-14% higher chlorogenic acid content than caffeinated green coffee beans, suggesting that the removal of caffeine can influence acidity even before roasting.
Interestingly, a 2022 study in the Molecules Journal found that despite sometimes having a lower pH, decaffeinated coffee often has a higher relative concentration of certain acids, like chlorogenic acid. This could contribute to a perception of increased acidity in taste compared to regular coffee, even if the actual pH is slightly lower. In fact, a 2013 study by Alexia N. Gloess in European Food Research and Technology reported there is no correlation between pH and perceived acidity in the flavor of different coffee brands and their products.
What Are the Best Low Acid Coffee Brands?
The best low acid coffee brands are those that have been scientifically verified to have lower acid levels than average commercial coffee. A recent study by Abdulhakim Sharaf Eddin from North Carolina A&T State University, published in March 2024 in Bioactive Compounds in Health and Disease, found that many brands claiming to be "low acid" or "acid-free" do not live up to their labels. Only one out of seven brands tested was significantly less acidic than average coffee and above the critical pH level that defines low-acid coffee. Surprisingly, some labeled as low-acid were actually more acidic than regular coffee.
So, how can you find coffee that truly delivers on its low-acid promise? One option is to look for dark roasts like Italian or French roast, which naturally have lower acidity due to longer roasting times. Many grocery stores offer these options.
Where to Buy Truly Low Acid Specialty Coffee?
For high-quality, specialty low-acid coffee, consider brands like Powerbean Coffee, known for their dark roast options such as decaf espresso and arabica. These blends offer a balanced acidity, full body, and flavors of dark chocolate, nuts, and spices.
How Can I Make My Coffee Less Acidic?
Making your coffee less acidic can be achieved by using brewing methods like cold brew, French Press, or Aeropress, which extract fewer acidic compounds. For those searching "how to make coffee less acidic", Choosing low-acid coffee varieties can also significantly reduce acidity.
